I think there's some story about how she was supposed to marry someone else, but Loki took his place and so Odin demanded that she remain faithful to Loki since she technically skipped out on her previous hubby-to-be and so she was one of the gods who support/aid Loki through like....everything and anything he did.

Lol that's what the Wikipedia thing said so...*shrug* I don't really know much of anything on Norse mythology other than the baaaare basics. I almost bought this book on it (which probably would have had more information about her)

This is both hilarious and cleverly contains little elements of the Norse mythology. I like the fact that Sigyn has a basin collection and that you used the line of 'I will break your every single bone'.